The diagram of the lawn and the shed is shown below.
The area of the lawn needed to be mowed equals to the area of the yard minus the area of the shed
The area of the yard =

The area of the shed =

The area of the lawn =

The area of the lawn =

The area of the lawn =
If the speed is constant, there is no acceleration. No acceleration, no force.
No shel will not have enough tile. If you don't know the dimensions of the actual tile how will you solve. If you have a closet 18 square feet it could be 9 ' x 2 ' = 18 square feet. If the tiles were 12" x 6" you would need 36 tiles. If the closet was 6' x 3' = 18 square feet you could have the tiles 12" x 6" = 36 tiles. So you need to know the dimensions of the tile.
To find what percentage one number is of another; divide the first number by the other number and multiply by 100 !
p = ( 6 / 76 )× 100 ;
p = 600 / 76 ;
p = 7.89 ≈ 8 ;
p% = 8% ;